The present invention relates generally to diesel particulate filters and, more particularly, to methods and apparatus for estimating soot loading in a diesel particulate filter.
Diesel particulate filter (DPF) systems are becoming more common in many markets, particularly heavy duty truck markets, and will likely remain as an important emission solution for particulate matter for some time to come. There are various methods to estimate the accumulated soot mass in the DPF but, currently, there is only one direct feedback mechanism, namely, a pressure drop (dP) sensor that measures pressure drop across the DPF.
The dP signal can be used to estimate DPF soot mass through a correlation or model, usually based on observation of numerous filters over a period of time, thereby establishing data for what shall be referred to as a “nominal” DPF. The model inputs have several uncertainties. Aside from typical sensor uncertainties such as offset, hysteresis, temperature drift, time drift, etc., there are additional factors that affect model accuracy. These factors include DPF-to-DPF variations, ash loading of the filters, non-uniform soot loading, catalyst sintering, and the like, all of which make it difficult to confidently compare pressure drop data of a subject filter with pressure drops across a nominal DPF to estimate soot loading of the subject DPF based on soot loading of the nominal DPF.
If soot loading of the subject DPF cannot be estimated with a reasonable degree of accuracy, then damage to the DPF may result, or the DPF may cease to perform acceptably to filter particles. If the estimated soot loading of the subject DPF is too low, then the subject DPF may be overloaded with soot before an active regeneration operation is performed, and the regeneration operation may not burn off acceptable levels of the accumulated soot. If estimated soot loading of the subject DPF is too high, then the subject DPF may be subjected to excessive regeneration operations, which can shorten its useful life.
It is desirable to provide a technique for improving the accuracy of soot loading estimates for DPFs.
In accordance with an aspect of the present invention, a method for estimating soot loading of a diesel particulate filter comprises establishing a soot loading model for estimating soot loading of a nominal diesel particulate filter, adjusting the soot loading model for a subject filter to account for differences between the nominal filter and the subject filter, and estimating soot loading of the subject filter using the adjusted soot loading model.
In accordance with another aspect of the present invention, a diesel engine with an exhaust aftertreatment system comprises a subject diesel particulate filter, and a controller, the controller comprising a soot loading model for estimating soot loading of a nominal diesel particulate filter, the controller being adapted to adjust the soot loading model for the subject filter to account for differences between the nominal filter and the subject filter, and being adapted to estimate soot loading of the subject filter using the adjusted soot loading model.